05 June 2016

Don't forget to Vote OUT in the referendum on June 23, 2016.....

Picture: not the Euro...

What do English roses have to do with the EU?  Very little except that the rose is a well-known symbol of England (see the tudor rose on the coin, left).

For information on where this blog stands on Brexit, please see the sister blog: http://whybritainsscienceisbetteroutofeurope.blogspot.co.uk

and also


27 September 2015

Choices, choices: what rose to buy in 1890

Old gardening magazine are full of advertisements by rose nurseries touting their wares, usually mentioning at least some of their stock. To take one (almost) at random, I reproduce here a Victorian advertisement from A. Lauer of 1210 East Broadway, Louisville, Kentucky, USA. It appeared in the "American Florist" magazine for March 1890.

It offers "healthy young plants in 2 and 2½-in. pots". Most were offered at $4 per 100 or $35 per 1000, but some (presumably considered a bit special, or perhaps a bit difficult), like 'Paul Neyron' and 'Général Jacqueminot' commanded the higher price of $6 per 100. Larger plants were available but for them you had to stump up $15 or $18 per 100.

What interests me about this list is how many of the plants are still commercially available (although admittedly you would have to search hard for most). For instance, of the first ten listed, nine (Perle des Jardins, Niphetos, Sunset, the Bride, Bon Silène, Sombreauil, Souvenir d'un Ami, Mme Scipion Cochet and Archduke Charles) still exist. Only poor Cornelia Cook seems to have been lost.

1210 East Broadway is now a nice residential area, but according to Google Maps (picture below) the rose nursery of 1890 is long gone!

Black spot of roses and its control

Rose black spot's Achilles heel

Every rosarian sooner of later has to take a position on black spot. Personally, I don't do much about it except try to grow resistant roses and break the over-wintering phase of the fungal life cycle. Otherwise I just put up with it, at least in modest amounts. I don't spray: but mainly out of indolence rather than conviction.
Late season black spot on Paul Neyron

Black spot's Achilles heel is its winter stage. To understand this fact, it is important to understand the life cycle.

Black spot is caused by an ascomycete fungus called Diplocarpon rosae. It reproduces mainly asexually by conidiospores (spores that produce an identical copy of the parent fungus strain). The other type of spore, ascospores, which are the ones that increase the strain diversity of the fungus, are rather rarely produced so I won't consider them further here. The propensity of black spot to reproduce asexually means that a region may be dominated by a particular strain for a long period of time. If a rose has blackspot in your area but doesn't somewhere else, it could be because of climate differences, but it could also mean you have a different strain of black spot.

Rose leaves when they emerge in the spring are free of black spot. To acquire the disease conidiospores have to contact the leaf. In summer, probably they will be splashed onto the leaf from an existing black lesion. However, in spring all the leaves are new and clean so conidiospores have to be splashed up from a decaying leaf on the ground that fell the previous autumn*. As raindrops hit dead leaves on the ground, fine droplets (aerosols) are formed which may pick up spores and waft them up the the leaves.

Many rose growers remark that their roses don't have blackspot early in the season but develop it in late summer. This isn't strictly true. It is just that there are very few lesions in the spring, but as each lesion spreads its conidiospores, one lesion becomes two, becomes four, becomes eight and so on. There comes a point, usually in late summer, when black spot is suddenly noticeable and ugly.

Control of black spot: winter treatments

When the infected leaves fall in autumn the fungus continues to survive on the dead leaves, lasting long enough to reinfect the newly emerging leaves with conidiospores in the spring. It is in winter that black spot needs to be attacked. The length of time the dead leaves can last as a source of infection depends on climate and soil conditions. A mild winter and biologically active soil can break down the dead leaves before spring arrives and before they can infect the new leaves. Wait until all the leaves have fallen and cover them with a rich mulch, or with manure, to encourage decay and a succession of other fungi and bacteria that will rot the leaves to the state beyond which they will be a source of infection. In spring, just before the new rose leaves open, put on a mulch of bark to isolate any remaining viable spores. Western red cedar bark is ideal as this bark has a mild fungicidal effect. Having broken the life cycle you will find it takes much longer for black spot to re-emerge in the spring. Of course it will come back eventually, from an occasional conidiospore drifting in the wind from some other source of infection, but you will have broken the back of it.

In former times, the life cycle could be similarly broken in winter by applying a fungicidal drench once all the leaves had fallen, to kill the conidiospores in the ground. I remember a beautiful bed of Apricot Nectar that had terrible blackspot one year in my family's garden. It was given a drench of Jeyes Fluid in winter and the following year not a single black-spot lesion appeared - it was almost miraculous. (Jeyes Fluid is an old-fashioned British disifectant made from coal tar). It never seemed to harm the soil or the plants, and the coal tar chemicals probably biodegraded quite quickly, but it was lethal for black spot.

Another line of attack is to increase the natural resistance of the plants. In my experience infection rates are much higher if the plants are stressed, whether drought stress or nutrient stress. A well fed and watered plant that is growing vigorously will have maximum natural resistance.

*(Another possible source of overwintering spores is on infected stems, but if your plant has such a bad case of black spot that even the stems are infected, the plant should probably be dug up and burned).

19 June 2014

Nuits de Young

Nuits de Young (more authentically "Nuits d'Young") is a moss rose of a sumptuous black-purple, and is one of the darkest of all roses. It is named, indirectly, after Edward Young, English poet and divine (1681 – 1765) whose nine part poem, "Night Thoughts", published between 1742 and 1745, made him famous. The poem is a brooding meditation on death, and so wholly suitable for the blackest of roses. The poem was an 18th century success, striking the same chord as the other romantics including Goethe. It was translated into many languages including French.

Rosa x alba "Maiden's Blush"

The various types of Rosa x alba (according to Hurst, a canina x damascena cross) are tough and vigorous. Miss Jekyll called it "a capital rose" and it was a great favourite of cottage gardens all through the 19th century. The double white forms Maxima and Semiplena are most commonly seen, but a beautiful pale pink form, Maiden's Blush, arose in the 18th century (usually the date of 1797 is given) - and quickly established itself as a great favourite. Mrs Gore could write in 1838 that "Our cottage and farm gardens adhere almost exclusively to the Cabbage Rose, Damask, and Maiden's Blush". Paul praised the "delicately coloured blossoms, and the ample cool-looking leaves which it supplies". There was soon an attempt to improve on Maiden's Blush, resulting in varieties like Celeste [Celestial], Félicité and La Séduisante. Madame Audot and Queen of Denmark also followed. The Victorians loved a delicate blush pink. The great rosarian Paul accordingly wanted to create a moss rose with the delicate pink colouring of Maiden's blush. He writes: "To obtain this I hybridised the Moss du Luxembourg with an alba Rose, and among the offspring was a Moss Rose with flowers like the Maiden's Blush, afterwards named 'Princess Alice'."

16 June 2014

Gloire de Dijon

One of the greatest roses of all time.

If one were designing a rose garden for the gods, "Gloire" would take its rightful place. Gertrude Jekyll called it "The most free-flowering of all climbing Roses, and for general usefulness has no equal." Henry Arthur Bright wrote: "But no rose, taking all the good qualities of a rose together, its hardiness, free blooming, beauty, and scent, will surpass the Gloire de Dijon, though the golden cups of Marshal Niel may be richer in colour, and the fragrance of La France recalls, as no other rose does, the luscious fragrance of Oriental otto of roses".

Gloire de Dijon (bred by Jacotot in 1853) is what may aptly be described as an "advanced noisette". It is a relatively free flowering scented climber. Its colour is basically buff - a sophisticated, unshowy but rich buff that is difficult to categorize and may vary, perhaps due to the soil or pH on which it is grown. Some growers pronounce in apricot, some yellow-buff. Some see tints of gold, others of pink. No-one complains when its lovely quartered blooms appear.

13 June 2014

Rosa forrestiana

This wild rose, from mountain scrub in Sichuan and NW Yunnan has (for a wild rose), unusually deep and bright red-pink flowers.

It only has a brief flowering period in June, but the decorative hips add interest through the rest of the year, so it is a good bet for an informal shrub border.

Collected in 1918 by the great George Forrest, it is one of the best of the wildings.